Method for producing pig iron or steel in blast furnaces



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Sept. 28 1926.

J. G. AARTS METHOD FOR PRODUCING PIG IRON OR STEEL IN BLAST FURNACES 2Sheets-Sheet 1 Sept. 28 1926. 1,601,015 J. G. AARTS METHOD FOR PRODUCINGPIG IRON OR STEEL IN BLAST FURNACES V Filed March 29. 1924 2Sheets-Sheet 2 u Tr 72, IMF

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" Patented Sept. 28, 192., v I

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JACOBUS GERARDUSAARTS, OF DONGEN, NETHERLANDS, ASSIGNOR TO AARTS-EISEN-AKTIENGESELLSCHAFT, F LUZERN, SWITZERLAND.

METHOD FOR PRODUCING PIG IRON OR STEEL IN BLAST FURNACES.

Application filed March 29, 1924, Serial No. 702,954, and in Germany May8, 1923.

My invention relates to an improved take place in presence of excessivequantities method of treating iron ores and ferriferous of carbon actingtoreduce again directl waste in a blast-furnace in order to produce theformed carbon-dioxid or carbonic aci pig-iron or steel. the more so asthe average temperature in a 55 a Theblast-furnace process hithertoaccomblast-furnace is above 1000 C., so that carplished is objectionablefor several reasons bonic-acid will decompose. or disadvantages. As cokeand iron-ore are The object of my invention is to remedy supplied to thefurnace in successive alterall of the hereinbefore mentioneddisadvannate layers, the two materials cannot mix cages of the old art.60 thoroughly and even in the bottom part of I am aware that electricalblast-furnaces the furnace they mix only very imperfectly. have beensuggested heretofore, which are Further the ore is owing to its piecedor provided with a short supplying tube or conlumpy shape mainly notaffected by the cardui-t mounted inthe mouth to depend therein bonmonoxide-gas (CO) except externally, so that the fuel may be fed inthrough said 65 that is to say, by contact with its outer faces tube,while the ore is supplied separately only, and this is particularlyprejudicial in from the fuel in the annular space surroundcase of hotagglomerated and fritted mateing said tube. Obviously as far as the tuberials as always present in blast-furnaces even or conduit goes, the twomaterials will deintemperature zones at 1200 to 1300 C. scend in thefurnace separately for the pur- 7 As a result of this incompletereduction the pose and with the result of producing in the oxides in theores, that have not been reupper portion of the furnace a coking0pduced, go into the slag which is formed in eration at a lowtemperature. In contradisthe bottom-zone of the furnace. Ore howtinctionthereto the essential and novel feaever, thus slagged or fritted,'cannotbe readtures of my invention are as follows. 7 ily reduced, so that thereduction must be I supply the ore and the fuel, with or mainlyaccomplished in the slag. This also without the required additions, toseparate refers to objectionable constituents, such as spaces in thefurnace, said spaces going sulphur, arsenic and so on. The iron mustdown as far as the boshes. The gases arisbe recovered from thesecompounds which ing from the boshes act to reduce in a dry 3 partly arehardly reducible, by the aid of way the ores mainly without primaryc'oal dissolved carbon. being present, whilst the fuel is subjectedConsidering this, the blast-furnace procto fractional distillation andcoked. The ess as hitherto carried out involves, that the ores and'thefuel having-thus undergone an main portion of the reducing operation isintroductory or partial reduction each of its 35 accomplished in a veryrestricted space and own, thereafter meet on the hearth where underunfavourable circumstances, especially the final or complete reductionof the ore, 1nin the molten mass where quite a multitude eludingmanganese, siliconand so on, takes of reactions take place which do notstart place, the metallic iron and the slag are from metallic iron butfrom iron oxid and melted and at the same time the Hon is car- 4 whichoccur while the reagents are in a buretted.

liquid state. It will be seen that in my improved meth- Due to thestated unfavourable circ umod tlie reduction of the ore and the cokingstances the quality of the produced pig-iron of the fuel to a largeextent or malnly are is deficient; but a still more objectionablebrought aboutin an operation separate from 4 particularity of the oldprocess resides in the melting operation, so that the process is theexcessive consumption of coal or coke, carried out under circumstanceswhichare since the principal reaction starts from solid especiallyadvantageous for obtaining apure carbon with the intermediate formationof roduct of better quality. The amount of carbon-monoxide andiron-carbide. uel supplied at the top of the furnace may 50 A furtherdrawback of the .old process be a multiple less, with relationto eachton, lies in the fact that all of the reductions than the weight oftheore whereby a considerable saving in fuel is realized. If desired orrequired the impurities, such as sulphur and arsenic, present in thecharge may be hydrogenized and volatilized, with the aid of the hydrogenproduced in the process, in the middle andlower part of the ore columnand in absence of any coal, so that such impurities are prevented fromgoing into the iron.

In the accompanying drawing wherein an approved embodiment of theinvention is illustrated:

Fig. 1 shows a. vertical sectionthrough the complete furnace,

Fig. 2 is a vertical section through the furnace with means for feedingthe fuel and the ore and conveying means for causing the ore to travelthrough the furnace.

Fig. 3 shows several crosssections through the furnace namely alonglines A-A, BB, CC, DD of Fig. 2,

Fig. 4 is a diagrammatic longitudinal section through thefurnace showingthe tem-" peratures for the zones at the various heights of the furnace.

'Coaxially to the vertical axis of the furnace is an inner shaft orchamber 6 within a larger shaft or chamber a of annular.

shape, the former receiving the fuel and the latter being supplied withthe ore, both with the required additions. The interior of the furnacethus comprises four zones I, II, III and IV, I being the melting zone,II being the coke generator, III being the ore shaft and IV being thefuel shaft. The raw fuel, with additions if required, is fed at the topof the vessel 0, Figure 2, and the ore with additions, if required, isfed into the surroundingfunnel d, and the supplied fuel and ore areconveyed from the funnel c and the funnel (Z to the fuel shaft and theore shaft respectively through descending tubes f and '9 provided withsuitable closures.

Obviously the blast-furnace may, if desired, comprise a plurality ofsuch reducing and coking chambers independently of each other. The orechamber III may be equipped, wholly or partially, with mechanicallyworking conveying devices, such as ro-- tary scoops or shovels forcontinuously transporting the ore from one story ,to the next lowerstory in counter-current to the gasesrising in wavy lines.

In the chamber IV the fuel gradually descends and in doing so it issubjected to fractional distillation and cokedby the heat of the risinggases, as will be described here inafter more in detail. The ore and itsadditions, if any required, are supplied at the top of the reducingchamberIII and gradually moved downwards in said chamber. During thisgradual downward movement the ore is wholly or mainly reduced just inaccordance with its particular nature.

In order to retain the descending ores within the reduction zone as longas possible and to bring them in constant and most intimate contact withthe ascending gases, the reduction room is equipped with stories ofstaggered or overlapping relationship, so that the gases are compelledto move in permanent counter-current with respect to the descendingores, the arrangement being such that the so-called dry reduction of theores and the expulsion of certain objectionable impurities will beensured thereby.

The reduced and purified ores travel from the lower end of the ore shafthaving a bottom k for supporting the weight of the ore through theopenings Z of said bottom into the chamber II in order to meet and bemixed with the coked fuel descending from the fuel shaft IV. In saidchamber II the reduction of the ores is completed, the iron and slagmelted and the iron carburetted, as far as such is required. The hearthis provided, as usually, with a slag, hole m, a tapping hole a andair-blast nozzles 0.

The ore on having been wholly or mainly reduced in the dry reductionchamber III at a temperature below 1000 0., mixes, still finelycomminuted, with the coke in the shaft or chamber II and is completelyreduced to ferrite, carburetted and melted down in the latter. Thereduction of the metallic oxids on the one side and the reduction of theimpurities, on the other hand, therefore, occur separately and underdifferent physicalconditions, that is to say, the former in a dry wayandthe latter in a melted" state, it being noticeable that the principalimpurities such as sulphur and arsenic, have been previously removedfrom the ore in a dry way in the chamber or shaft IIIas will behereinafter described more in detail. F 7

It is advisable to inject steam through the radially arranged or.distributed pipes 7) into the lower part of the fuel shaft or chamberIV, which part is heated above 1100 C. The steam rises within thechamber IV together with the carbon-monoxid gases ascending from thehearth II and produces on meeting the-incandescent fuel water-gas.Instead of steam or together therewith, if required or advisable in theparticular conditions of the case, wastegases containing carbonic acidand discharged from the ore shaft or chamber III through the openings 9may be introduced into the fuel shaft IV at the bottom thereof for thepurpose of reducing the carbonic acid contained therein and toregenerate the said waste-gas. P

Further it will be advisable to introduce the gas discharged from theshaft IV through the openings r after separation from its valuableconstituents, into the shaft III- partly be employed for the reductionof the ore, but they have a temperature of between 1400 and 1500 (l,which is too high for the ores, since the latter would be fritted andthe slag melted thereby. It, therefore, is necessary to reduce thetemperature of the gases and for this purpose I utilize in my improvedmethod mixed gas issued from the coking chamber and purified, which doesnot contain any by-products.

In this manner I alse realize the importantadvantage of having a gasrich in hydrogen and oversaturated with carbon in the reduction chamber.Hydrogen combines with sulphur, arsenic and the like and the gaseouscompounds thus formed are carried awaywith the gas current. Moreover thehydrogen greatly assists in the reducing process and just in this pointmy improved method is essentially distinguished from the customaryblast-furnace method, for-hydro-, gen is the most efficient reducingagent I known in the art.

'As the reduction of the ores is of great importance and acharacteristic feature of my new method, I deem it necessary to explainin detail the single operations thereof.

The hot carbon-monoxid gases rising from the lower part of the furnaceare mixed with the cool gases derived from the by-product, recovery forthe reasons hereinbefore mentioned, whereby, as above explained, apractically carbonic acid-free gas rich in hydrogen and oversaturatedwith carbon will be obtained, which comes in contact with the alreadyreduced ores at a temperature of 950 C. The hydrogen which, as is known,acts as a reducing agent even at low temperatures, did already createmetallic iron in the upper zones of the reduction shaft. Upon meeting agas rich in carbon-monoxid and containing hydrocarbon this gas will actas a catalyzer and the catalyzing action will be very eflicient owing tothe enormous constantly increasing and varying surface of the gas.Amorphous carbon precipitates upon the metallic iron, and, as suchcarbon forms at a low temperature, it is evidently carbon of highestactivity and of carburetting property. The thus formed iron-carbid-Fe C.is a still more active or eflicient reducing agent and adapted toreduce, together with the said a-carbon present, the iron and oxygencompounds still existing below the metallic surface of the ore. In thisway carbonic acid respectively carbon-monoxid forms, while the 11011carbid is reduced to metallic iron, which in turn acts as a catalyzerand again receives active carbon. This circuit action continues untilthe ore particles are completely reduced. As the ore advances to, thehigher temperature-zones, theless active'fl-carbon forms at temperaturesabove 600 C. acting to carburet the iron preliminarily and to protectthe same from subsequent melting with the slag.

My improved blast-furnace method may be divided into four separateelements according to the four zones I to IV of the furnace (see Figure4) (1) The lower hearth.-In the lowerhearth the molten mass or bathconsisting of iron and slag is intended to be brought to a temperatureof about 1500 C. and maintained at such temperature, until the mass isdischarged by tapping. Over and above the bath theoxidizing zone ofthehot vent prevails which, however, cannot .exert an oxidizing actionto any noticeable degree on ac,- count of the great speed of thedropping metal. i

- (2) The upper-hearth.-In this part of the furnace the followingoperations shall gas.

(3) The reduction 07zambe1".In this part of the furnace the followingoperations are to occur, viz:

(a) The dry reduction of the ore with the aid of the described gasmixture at a temperature not above 950 C.

(b) The hydrogenization of the impurities of the ore, in particular ofsulphur and arsenic, as above described.

The reduction chamber, if constructed to be of annular shape, is furtherdesigned with a view to avoid any losses of heat from the coking chamberthrough radiation;

(4) The coking okam'ber.In this part of the furnace the followingoperations take place, viz: a

(a) The fractional distillation of the fuel at a temperature graduallyrising from the tamperature of the atmosphere up to 1300 (b) ,In thelower part of the shaft, where the temperature is between 1100and 1300(I, the production of water-gas and the reduction of the temperature tothe limit suitable for a satisfactory coking process.

(0) In case that conditions allow, the regeneration of a part of the gasdischarged from the shaft and introduced atthe bottom of the coal shaft,oriof foreign gases of the kind, either alone or, together with theproduction of water-gas at temperatures of 1100 to 1300 C.

In this regard it is to be noted that the distillation of the coal takesplace endothermically i. e. in a heat consuming manner,

ment are saved;

(2) Saving of losses of heat arising from reheating and drying the cokein the blastfurnace;

(3) Saving of losses arising from cool-' ing, loading, piling,transporting and charging the coke;

(4) Saving of cost for transporting or conveying materials from the cokeoven to the furnace,

\ (5) Avoiding deterioration of quality of the coke at the pressing,loading, transporting and charging operations;

(6) The coal to be coked is heated, without any expense andwithout'combustion of gas by the large amount of the available hotgases, so that the gases otherwise required for heating the coke ovenare available for other purposes; moreover they bring about anabsolutely ideal-distillation by preserving all of the distillates, nomatter whether obtained at high or at low temperatures, and preventingtheir premature liquefaction or decomposition; in this way the out putis greatly increased, as regards both quantity and value thereof, a factwhich further assists in lowering the price of the coke going into thefurnace and of the iron produced.

(7 The method is restricted to the recoveryfrom the waste-gases of thecoking chamber of ammonia andof those hydrocarbons, which when cooledare liquid and to the desulphuration of said hydrocarbons, if required.In this way a gas is obtained which is practically free from carbonicacid, poorer than normally in nitrogen, rich in hydrogen andover-saturated with carbon. A gas of this sort is a most etficientreducing agent for iron ores and a most efficient carburetting means formetallic iron, but it has never been used or available in the art ashitherto practiced.

For hydrogen is a reducing agent which is not only by far more efiicientthan car bon-monoxid, but also active at lower temperatures as comparedwith thelatter, and further hydrogen acts to combine with 'veryobjectionable impurities, such as sulphur and arsenic, forming gaseouscompounds therewith, which are easily removed, sothat iron of greaterpurity and higher value will be obtained.

Moreover owing to the enrichment with carbon monoxid and hydrocarbon anover saturation with carbon is obtained so that active, amorphous carbonmay be formed in abundance which will act to greatly promote thereduction of the ironoxygen-compounds even at low temperature;

(8) The coke need not be of a certain high quality, since it has not tosupport the heavy weight of the ore and additions. Consequently the cokeis not subject to crushing and rubbing, so that also coal of lessvaluemay be employed in the furnace;

(9) In order to ensure a ready, quick and thorough reduction of the oresat low temperature, the ores must be finely comminuted. Consideringthis, there now is a possibility of utilizing ores on stock, which atthe present state of the art, cannot be used for the purpose on accountof their pulverulent state, or which otherwise must be previouslybriqueted in order to be in a treatable state, which, however, involvesconsiderable extra costs;

(10) By causing the just mentioned rich and cold waste or by-productgases to mix with that portion of the carbon-monoxid containing gasescoming from the upper hearth, which is intended to flow through thereduction chamber and which is of a detrimentally high temperatureinvolving the danger of the ore particles getting coated with a layer offritted or molten slag impermeable to the gas, a considerable reductionof the temperature is ensured, which will remove such danger. Apart fromthat the reduction of the ore particles commences, owing to the presenceof reducing agents, which are even active at low temperature, in theupper stories of the reduction chamber and immediately thereafter thecarburation of the produced metallic iron begins.

(11) Not only the costs of the unnecessary coking plant are fully savedbut also the costs to be invested inerectin the blastfurnace areconsiderably reduced. In furnaces of the kind hitherto constructedenormous quantities of the very voluminous coke must slowly move downfrom the top to the bottom of the furnace, before the coke is in therequired state of combustion, for the reason that the coke is chargedtogether with the ore in alternate layers and cannot advance except independence upon the speed of the movement of the ore..

In my improved method, however, the deseending movements of the twomaterials are independent of each other and the fuel is free to movedown at a greater speed. Consequently the portion of the furnacerequired for the reception of the fuel is comparatively small, whichinvolves a considerable reduction of the costs to be invested in theconstruction of the furnace.

(12) All of the aforementioned savings in fuel involve further reductionof the room required for the fuel, and particularly an enormousreduction of the cost of production of the iron.

From the foregoing, it is believed, that the advantages and novelfeatures of my invention will be readily understood and, therefore,further detail description is deemed unnecessary.

It will be evident, however, that my invention may be varied and adaptedin many ways, according to the several requirements desired, or mostsuitable under the different circumstances.

l/Vhat I claim is: 1. A method of producing iron in a blas furnace,consisting in feeding the ore in some cases with additions downwardlythrough the blast furnace in an ore shaft and out of contact with solidfuel,-feeding the ber, passing steam into the lower portion of the fuelchamber, supplying gas from the upper part of the fuel chamber to thelower portion of the "ore shaft for reducing the grains of ore to ironsponge, and bringing the reduced ore into contact with the coke producedin the fuel chamber in the bosh of the furnace so as to melt down theiron and simultaneously carburize it.

2. A method of producing iron as claimed in claim 1, characterized bythe featurethat the temperature of the gases servingforf carrying outthe reduction process is fixed by mixing the cooled gas derived from thefuel shaft with the hot gases which rise from the melting zone of thefurnace.

3. A method of producing iron as claimed in claim 1, characterized bythe feature that simultaneously with the steam, a portion of the gaseswhich pass out of'the' reduction shaft is introduced into the fuelshaft.

In testimony whereof I aflix my signature.

J AGOBUS GERARDUS TS.

